heisenbug

Slang for a software bug which fails to manifest itself during debugging.

The word is a play on Werner Heisenberg, a German theoretical physicist who devised the uncertainty principle, which states that "any attempt to measure the position of a subatomic particle will disrupt its movement, making it harder to predict."

Heisenberg is also the pseudonym of chemistry teacher turned drug kingpin Walter White in the television show Breaking Bad. Geeks say that the behavior of Mr. White, a.k.a. Heisenberg, could be likened to both the subatomic particle in the uncertinty principle and the elusive heisenbug.